The present disclosure relates generally to circular knitting machines, and more particularly to circular knitting machines having a fabric scanner mounted for contacting an inner surface of the fabric tube being knitted in order to detect defects such as holes in the fabric.
In a circular knitting machine, a tubular fabric is continuously knitted from a plurality of separate yarns. The tubular fabric potentially can include defects from various causes, and if a defect appears, it can be of a recurring type that will continue to be produced repeatedly. Accordingly, it is advantageous to be able to detect defects so that the machine can be stopped and the cause of the defect found and corrected before further production is resumed.
It is common practice to include a fabric scanner for scanning the fabric to detect defects. For example, it is known to mount a scanner on an arm that is affixed to a hub mounted on a vertical central shaft that extends down the center of the knitting machine. The tubular fabric also rotates about the axis of the shaft as it is being knitted. The tubular fabric thus moves in a screw-type fashion (i.e., both rotating and translating). However, the hub of the scanner mount does not rotate, and thus the scanner is fixed in one position. The scanner is long enough in the axial direction so that any defect will pass directly in front of the scanner at least once as the tubular fabric rotates.
Typically, the scanner actually contacts the inside surface of the fabric tube. Some defects (e.g., holes) can be of a nature that can cause the fabric to snag on the scanner. If this happens, the fabric can exert enough force on the scanner to damage it or its mount.